Commitments and Contingencies (Narrative) (Detail) shares in Millions		1 Months Ended												3 Months Ended
	Oct. 31, 2014 Facility MGD	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	May 31, 2022 shares	Aug. 31, 2021 shares	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Oct. 31, 2020	Nov. 30, 2019 gal	Jun. 30, 2018 USD ($)	Sep. 30, 2017 Petition	Apr. 30, 2017 Petition	Aug. 31, 2016 T	Mar. 31, 2023 USD ($) Indicator Product Facility	Mar. 31, 2022 USD ($)	Dec. 31, 2022 USD ($)
Loss Contingencies [Line Items]
Electric generating stations with water withdrawals under CWA | MGD	125
Electric generating stations with water withdrawals with heightened entrainment analysis under CWA | MGD	2
Number of DESC facilities subject to final regulations | Facility	5
Number of DESC hydroelectric facilities subject to regulations | Facility	5
Measurement of groundwater withdrawals | gal									3,000,000
Number of manufacturing gas plant decommissioned sites that contain residues of byproduct chemicals | Product														4
Estimated environmental remediation activities at manufacturing gas plant sites														$ 21,000,000
Environmental remediation costs recognized in regulatory assets														$ 38,000,000
Number of facilities inactive subject to final rule | Facility														3
Reserves for litigation and regulatory proceedings														$ 88,000,000		$ 94,000,000
Insurance receivables														72,000,000		68,000,000
Proportionate ownership share in project										100.00%
Proposed assessment amount from SCDOR audit										$ 410,000,000
Litigation settlement expense awarded							$ 165,000,000
Real estate transfer to satisfy obligation under settlement			$ 51,000,000
SCDOR [Member]
Loss Contingencies [Line Items]
Fair value of certain additional utility property transferred																3,000,000
Fair value of certain non-utility property transferred		$ 28,000,000
Fair value of certain utility property transferred														10,000,000
Gain from transferred utility property														9,000,000
Gain from transferred utility property, after tax														7,000,000
Common Stock | Dominion Energy
Loss Contingencies [Line Items]
Litigation settlement through cash						$ 43,000,000
Shares issued on settlement | shares				0.9	0.6
Dominion Energy South Carolina, Inc. | SCDOR [Member]
Loss Contingencies [Line Items]
Gain on expected transfer of utility property upon completion														10,000,000
Impairment of Assets and Other Charges | Dominion Energy South Carolina, Inc.
Loss Contingencies [Line Items]
Impairment of assets and other charges														$ 0	$ 0
Unfavorable Regulatory Action | CWA
Loss Contingencies [Line Items]
Number of mandatory facility specific factors. | Indicator														5
Number of optional facility specific factors | Indicator														6
Personal Injury or Wrongful Death Cases
Loss Contingencies [Line Items]
Reserves for litigation and regulatory proceedings														$ 72,000,000		68,000,000
Insurance receivables														$ 72,000,000		$ 68,000,000
Carbon Regulations [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Significant emission rate per year CO2 equivalent | T													75,000
EPA
Loss Contingencies [Line Items]
Number of petition agreed for reconsideration | Petition											2
EPA | Unfavorable Regulatory Action | CWA | Final Rule to Revise Effluent Limitations Guidelines for Steam Electric Power Generating Category
Loss Contingencies [Line Items]
Number of separate petitions for reconsideration granted | Petition												2
EPA | Minimum [Member] | Unfavorable Regulatory Action | CWA | Final Rule to Revise Effluent Limitations Guidelines for Steam Electric Power Generating Category
Loss Contingencies [Line Items]
Loss contingencies Individual circumstances period								2021
EPA | Maximum [Member] | Unfavorable Regulatory Action | CWA | Final Rule to Revise Effluent Limitations Guidelines for Steam Electric Power Generating Category
Loss Contingencies [Line Items]
Loss contingencies Individual circumstances period								2028